Arterial puncture needles are used in particular to permit introduction of a catheter into an artery. The catheter is advanced into the artery by sliding on the needle which guides it (called the short catheter method) or by sliding on a metal guide introduced beforehand into the artery via the puncture needle (called the Seldinger method).
The practitioner using the arterial puncture needle knows that the needle is in fact in place in the artery by observing the blood exiting from the needle. In particular, the blood will have pulsatile flow if the needle is in an artery.
For visualizing the pulsatile flow of blood without risk of the practitioner coming in contact with the blood, it is known, in the case of a short catheter, to provide the needle hub with a tubular and transparent viewing chamber. This chamber is accessible, via an inlet end, to the reflux of blood in the needle and closed at an opposite outlet end by a plug which is leaktight to the blood but permeable to the air.
The arterial pressure, which is greater than the atmospheric pressure, causes the reflux of blood to completely fill the viewing chamber once the needle penetrates into the artery.
If the puncture is to be repeated, the practitioner can remove the plug in order to empty the chamber and thereafter can put the plug back in place. In such a case, the practitioner is unable to monitor the new introduction of the needle into the artery because the walls of the viewing chamber are already red with the blood from the previous puncture. On the other hand, the practitioner can leave the proximal end of the needle open allowing the blood to escape freely from the hub.